The invention pertains to a method for a transfer system with workpiece carriers. Such a transfer system has, for instance, become the object of DE 195 32 281 A1. This known transfer system involves a track-guided system in which the corresponding workpiece carriers travel along the track in grooves on a plate that is constructed in a modular manner from individual plates. This known workpiece carrier features a read-write head for data transfer, with which the workpiece carrier communicates with associated individual stationary read-write heads distributed on the track. Also arranged on the known workpiece carrier are one or more distance sensors in order to permit communication of the individual workpiece carriers traveling in succession on the track. Thereby a collision of individual workpiece carriers is to be prevented, so that backed-up operation of these workpiece carriers on the transfer system is possible.
The disadvantage of the known transfer system is that the data-loading stations in the form of the known read-write heads are arranged distributed along the track, whereby an extraordinarily high programming and circuitry expense results. Such a read-write head is assigned to practically every machining station, which causes the disadvantage that the necessary information must first be fetched before each machining station, in order to communicate to the workpiece carrier what control processes are expected of it and what machining processes are to be carried out by the machining station. The known workpiece carriers have only a limited intelligence, because they are not freely programmable, that is to say, they must fetch the appropriate information and control commands before each machining station. It is not possible, for instance, to associate in advance a given travel behavior with a workpiece carrier over the entire track, not even, for instance, a given travel priority. The arrangement of read-write heads, moreover, presumes that the workpiece carrier is arranged directly opposite a stationary read-write head in order to guarantee a transfer of information at all. This is associated of course with the disadvantage that a prospective control of the workpiece carrier in conjunction with components of the transfer system is not possible. For instance, it is not possible for this workpiece carrier to prospectively trigger switches and other control elements on the track by wireless means so as to encounter a given constellation of the transfer system as it approaches. The arrangement of such read-write heads thus has the essential disadvantage that the workpiece carrier must be stopped for each information transfer in order to achieve a precisely opposite positioning of the workpiece carrier to guarantee the transfer of information. This prevents a rapid travel operation on the track and an information transfer of high information density.
The invention is thus based on the problem of refining a method for operating a transfer system with workpiece carriers, and a transfer system operating according to this method such that a separate, individual intelligence can be associated with each workpiece carrier, and thus a considerably more rapid and economical operation of the transfer system and the workpiece carriers is possible.
The core of the invention is thus that each workpiece carrier takes on information intended for it wirelessly from the data-loading station, the information is written into a microprocessor memory on the workpiece carrier, the written information, together with basic data present in the microprocessor, is converted into a travel and machining program for the workpiece carrier, and the workpiece carrier independently conditions its predetermined travel path on the basis of the travel and machining program, travels to corresponding machining stations and exchanges data with machining and/or positioning stations arranged on the path.
With the technical teaching provided, the essential advantage is achieved that a workpiece carrier is provided with completely autonomous intelligence which is fed to it from essentially one single data-loading station, preferably by wireless means. This permits an autonomous travel and machining operation for each workpiece carrier. It goes without saying that the present invention is not limited to the provision of a single data-loading station. It is possible, particularly in case of large transfer systems, for several data-loading stations to be distributed along the path. Of importance for the present invention, however, is that a data-loading station need not be associated with each individual machining station, as is presumed in DE 195 32 281 A1, but rather, information is fed to the workpiece carrier initially and essentially only one time, in the form of program and information data, which it retains across the entire transfer line system.
There is thus the advantage that, because of the retention of this information, additional data transfers need no longer take place, because the workpiece carrier is so intelligent that it can travel to all machining stations independently, or pass them by, and its intelligence also suffices to condition and prepare the travel path that it is to take. In order to process the stored data, the workpiece carrier possesses a microprocessor control unit.
Additional advantages and refinements of the invention are the objects of the dependent claims.
Thus the workpiece carrier not only controls its own travel operation with respect to defined machining stations arranged stationary along the path, it also conditions the travel path provided for it. This includes, for instance, traveling on side tracks, controlling switches to travel such side tracks and the parameterization of machining stations. This is understood to mean that it contains certain information in its control program which it passes on to the machining station or possibly that it receives information from the machining stations that is intended for it or subsequent machining stations.
As an example here, one could mention that it obtains a certain characteristic in the information acquisition from the data-loading station, for instance, that the workpiece carrier with the workpieces on it is intended only for drill machining. A xe2x80x9cdrillingxe2x80x9d workpiece carrier of this type now conditions the machining stations it moves to, and which are responsible for it. It then informs the machining station of, for instance, the necessary drilling depth and all other machining steps that are necessary to machine the workpiece seated on it.
In the next pass, the workpiece carrier can then take on other information from the dataloading station which instruct it to supply the workpiece seated on it to certain assembly processes. It can thus be programmed individually for the machining designated for it, without having to take on any additional commands along the track.
In the same manner, the conditioning of the track with this intelligent workpiece carrier can also take place in that, during the approach of the workpiece carrier to certain track elements, a wireless signal transmission from the track elements to the workpiece carrier and back takes place in order, for instance, to reset switches or to prepare the machining station for the fact that the workpiece carrier is arriving. In this manner, the machining station is prepared for a passthrough or a stop with the associated machining operations.
With the technical teaching as presented, there results for the first time the advantage that every workpiece carrier can be set up individually for a given machining, its intelligence applying for the duration of the passage through the entire transfer system. It goes without saying that such an intelligent workpiece carrier can also pass through the transfer track system several times without having to take on new information. Thus a very rapid travel operation results, because the workpiece carrier automatically controls the manner in which it travels, based on its input intelligence, without having to take on additional intelligence from the track.
This thus yields the additional advantage that it is now possible to machine so-called individual lot sizes with one such workpiece carrier.
An additional advantage of the invention lies in the fact that the workpiece carrier is constructed to be self-teaching, that is, it has a self-teaching intelligence. After taking on the information in the data-loading station, it can occur that congestion, a fault or incorrect machining takes place in one of the machining stations to be visited in the future. The workpiece carrier now present there in the faulty machining station wirelessly reports a congestion alert along the track to the successive workpiece carriers, stating more or less that the machining station cannot be visited.
Now when a workpiece carrier situated in the data-loading station departs, it receives a congestion alert from the workpiece carrier located ahead of it and alters its travel program such that it remains on the transfer system only for a certain distance, without colliding with the workpiece carrier situated ahead of it. Then, for instance, a wait cycle is inserted, which lasts until the machining station can again be visited.
The self-teaching effect can even extend so far that, in the adoption of information in the data-loading station, it is also programmed in that a certain sequence of machining steps is not necessary. In this case, the intelligent workpiece carrier can also pass through a faulty machining station without any machining taking place, and could then travel immediately to the next machining station in order to have its additional machining steps performed there.
Another essential advantage of the invention is that no higher-level control computer for controlling the entire travel operation is necessary, because each workpiece carrier contains its own separate intelligent sequence program for itself and behaves intelligently on the track assigned to it, that is to say, it avoids congestion, it waits and it conditions the track according to its own installed program. For instance, the computer that supplies the data-loading station with the respective control program for the workpiece carrier does not know where the respective workpiece carrier currently is located on the track. Only the control unit of the workpiece carrier itself knows that, so that a considerably simpler programming effort is provided, precisely because a higher-level control computer managing the entire track is no longer necessary.
The object of the present invention results not only from the objects of the individual claims, but also from the combination of the individual claims with one another. All data and characteristics disclosed in the documents, including the abstract, in particular, the spatial configuration represented in the drawings, is claimed as essential to the invention, insofar as it is novel with respect to prior art, individually or in combination.